168

MODERN PAPER-MAKING

The length of the wire depends on various circumstances, chief of which
are the speed of the machine and the quality of the paper. It is obvious that
the longer the wire the more water will drain from the stuff through the action
of the tube rolls before it reaches the suction boxes. Hence for heavy sub*
stances and rag papers a long wire is indicated, to run at an economical speed.
On the other hand, if banks have to be made on the same machine, too little
water would be carried to the dandy roll to have a good control of the water-
mark. Therefore a compromise has to be made, and the length of the wire
has to be decided by all the circumstances, including very often the space
available. From 40 to 60 feet give good average results, with from 16 to

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FIG. 53 FIG. 54

[The United Wire Works Ltd.

53 AND 54,—PHOTOGRAPHS AT THE SAME MAGNIFICATION OF PLAIN WEAVE AND SUPERFINE

WEAVE 72 MESH

30 tube rolls, according to their size and the speed at which the machine is
to run.
This question of length of machine wire has always been a subject of con-?
troversy among paper-makers, but before stating definitely what length of wire
is most suitable for a machine making certain classes of paper it is necessary
to take a variety of subjects into consideration.
Other things being equal, the machine on which very wet or highly fibril-
lated stock has to be worked will require a longer wire than one on which only
free stuff is worked.
The reason for this is that the wire is simply a filter for removing the water
and receiving the fibre deposit upon its surface. It is true that the sheet or